1. Field of the Invention
This invention relates to banding apparatus of the kind comprising means for supporting at least one object to be enwrapped by banding material, means for feeding banding material to said object, means for enwrapping this object with the banding material fed thereto, and a device for tightening the banding material disposed around said object, the improvement whereby the tightening device comprises a piston-cylinder unit operable by compressed air through a conduit incorporating an adjustable valve disposed around said group.
2. Description of Problem and Prior Art
Banderolling apparatus of this kind is used, inter alia, for wrapping or enfolding one or more objects for sales purposes. It is particularly desirable in sales units of this kind that the banding material shall hold the individual packages or the like firmly so that they cannot be pulled out or inadvertently detached. Usually this can only be achieved if the banding material wrapped around the object or package is pulled taut before being welded, gummed or otherwise fastened.
It is known to effect this tightening by feeding the banding material via a roller with a driving means which is brought into play at the appropriate moment to pull back the banding material in the direction towards its point of introduction and thereby tighten it. The drive in this case is performed through an electric motor and a slip clutch.
Correct tightening creates difficulties when the number or kind of objects which are to be packaged vary. Objects which cannot be deformed are generally dealt with using a greater degree of tightening, but the available length of pull is comparatively small and only a small length of banding material can be pulled. Soft packages, for example stocking packages or the like, permit or require the use of less force. The length of banding material which is to be retracted is, however, usually greater. A driving combination consisting of an electrical motor and a slip clutch can only meet the contrasting demands imperfectly. Accurate adjustment is difficult, especially as the functioning is made variable by continuous and lengthy operation producing heating effects, or because of the appearance of wear.